Initial stages of the epitaxial growth of Pr2O3 on Si(1Â 1Â 1) studied by LEED and STM

The initial stages of the molecular beam epitaxy growth of Pr2O3 on atomically clean Si(1 1 1) have been studied in ultra-high vacuum by low energy electron diffraction and scanning tunneling microscopy. At very low coverages, the oxide nuclei decorate the dimer rows of the silicon surface as line structure forming open triangles. At higher coverages, two-dimensional, equilateral, triangular islands with a fairly narrow size distribution and a well defined thickness are observed. Island nucleation occurs both at step edges and on the terraces. Upon coalescence at coverages beyond one monolayer, the surface is covered by a flat and pseudomorphic oxide film with a (1 × 1) surface unit cell.